In a large saucepan, heat oil and butter.
Saute onion, celery, carrot and garlic in oil and butter until onion is golden.
Add tomatoes, oregano, thyme, basil, salt, pepper and sugar.
Bring to a boil.
Cover.
Simmer 1 hour.
Uncover and simmer 1 hour longer.
Sauce may be stored in refrigerator 1 week or sauce may be frozen.
Makes about 4 cups.